1) Field of the Invention
The present invention relates to a technology for predicting collision of objects by using an image sensor and a millimeter-wave sensor.
2) Description of the Related Art
Vehicles are now an essential item in the human life. In the meantime, many lives and assets are lost due to traffic accidents. Therefore, a safety operation system is reviewed. Particularly, various kinds of techniques are proposed to support safe operation and to prevent traffic accidents in a vehicle warning device of the safety operation system.
For example, there is a method of measuring, with an ultrasonic sonar, a distance between a vehicle and obstacles around the vehicle at the time of parallel parking the vehicle. However, when a relative velocity between the obstacle and the vehicle is large, the distance measure with the ultrasonic sonar is not accurate. Therefore, this method is not suitable during a normal running of the vehicle. There is also another method of detecting, with a millimeter-wave sensor, an obstacle during normal running of the vehicle, and warning a driver about the obstacle. However, in this method, a distance between the vehicle on which the millimeter-wave sensor is mounted (hereinafter, “own vehicle”) and the obstacle can be detected, but a possibility of a collision between the own vehicle and the obstacle cannot be detected.
In a signal processing method of a millimeter-wave sensor described in Japanese Patent Application Laid-open No. 2002-257927, a scanning is carried out using a beam of the millimeter-wave sensor in addition to detecting a distance between a physical object and a own vehicle. This makes it possible to detect a moving direction of the physical object, and one sensor can detect a distance to the physical object, a sped of the object, and a moving direction of the object.
A vehicle control device described in Japanese Patent Application Laid-open No. 2001-257927 makes a marker of a vehicle in the front flicker, and obtains information about the front vehicle from the marker, by using an image sensor that an own vehicle has. With this arrangement, a distance between the own vehicle and the vehicle in the front is calculated, and the run of the own vehicle is controlled.
However, according to the conventional technique disclosed in Japanese Patent Application Laid-open No. 2001-143199, the millimeter-wave sensor requires the function of scanning using the beam of the millimeter-wave sensor, resulting in high cost. Further, an erroneous recognition of an obstacle due to a reflection from a road surface or the like cannot be decreased sufficiently.
According to the conventional technique disclosed in Japanese Patent Application Laid-open No. 2002-257927, unless a predetermined marker is mounted beforehand on the vehicle running ahead of the own vehicle, distance between the two can not be detected.